Our invention pertains to an encoder for propulsion train line apparatus for use in a train speed regulation system. More specifically, the invention pertains to an encoding arrangement which receives and encodes propulsion commands to energize the proper combination of control relays to achieve a desired speed level for a train or to activate a train braking function if the propulsion level is reduced below zero.
In the prior art technology in rapid transit train operation, use is made of a parallel-series tractive effort control system. In this arrangement, the four propulsion motors and associated control resistors on each car are initially connected in series across the power source in what is known as the "switch" condition. To increase the power and thus the speed, the resistance is cut out in selective steps and then the motor fields are weakened. To further increase the tractive effort, the motors are switched into a parallel-series combination, normally with two pairs of paralleled motors connected in series, together with the resistors, across the source of power. Once again, further speed increase is obtained by cutting out the resistors in steps and thereafter weakening the fields of the motors. Obviously, except for a complete shut-off of the motors, train speed is reduced by the reverse order of these stepping actions. Originally, and still in use in some older rapid transit systems, the motorman or operator of each train manually controls the train speed from a single position in the lead car using switching contactor apparatus. Each car is controlled simultaneously to the same propulsion condition through train line wires running the length of the train and automatically connected from car to car when such cars are coupled together to form a single train. Subsequently, a variable control of propulsion effort was developed in which variations of the propulsion level exist throughout the train. In other words, the levels of propulsion effort on each car may be independent of the levels obtained or existing on other cars. For example, the control arrangement may be such as to cut out the propulsion effort altogether on every other car in order to provide additional variation or steps in the propulsion level. More sophisticated variable control systems are now being requested. In one, each car of the train may be individually advanced or retarded to the next higher or lower propulsion effort, respectively, than that established by the propulsion train line arrangement. Such changes in the propulsion effort will be stepped car by car from the lead car to the last car of the train under the control of so-called advance train line apparatus over a separate train line channel. For example, one such arrangement is disclosed in the copending application for Letters Patent of the United States, having the same assignee and filed the same date as this present case by R. H. Grundy for an Advance Train Line Register For A Train Speed Regulation System, Ser. No. 581,370. In this type of variable speed control, the propulsion train line apparatus must then respond to the completion of each full train step by step variation cycle and encode these advance train line cycles into a base condition of the propulsion train line apparatus to reflect the new propulsion level of the entire train.
Accordingly, an object of our invention is an improved propulsion train line control apparatus for trains which is responsive to the achievement of preselected conditions in the variable propulsion levels within the train cars to establish a new propulsion level base for future variations.
A further object of the invention is a propulsion train line encoder responsive to the completion of a cycle of car by car changes in the propulsion condition of the train to establish a new train base propulsion level.
Another object of our invention is a propulsion train line arrangement for a rapid transit train which receives and decodes periodic input signals marking the completion of step by step variation cycles in the propulsion level and which encodes a signal to the propulsion train lines to establish a preselected propulsion level equivalent to that achieved during the last completed cycle.
A still further object of our invention is an encoder arrangement for propulsion train line control apparatus which receives input signals designating completion of each cycle of car by car variations in propulsion level, records the number of cycles completed, and changes the existing base propulsion level at the end of each cycle.
Yet another object of the invention is propulsion train line apparatus for rapid transit trains normally responsive to completion of each cycle of car by car variation in the train propulsion level to advance the base propulsion level for the train and which is responsive to a preselected tabulation of train propulsion limitations in accordance with the allowed speed signal to limit the train speed and to transmit a signal to the advance train line register to inhibit further cycles of operation.
A still further object of the invention is propulsion train line apparatus for a rapid transit train responsive to stepped variations in train propulsion level to periodically reset the base propulsion level for further variations and to the detection of the lowest speed rate to actuate a braking control apparatus to initiate brake action and to inhibit advance train line apparatus from attempting a subsequent down count.
Still another object of our invention is propulsion train line encoder apparatus for trains including a reversible counter to register advance train line clock pulses, counting up or down in accord with the direction of speed error, driver means to actuate the train line channels to condition the propulsion apparatus on each car to establish a new train base propulsion level, converter logic to translate the BCD counter output to a decimal signal for the driver means, and inhibit logic to halt counter operation when the maximum limit is reached in converter logic output.
Other objects, features, and advantages of our invention will become apparent from the following description and accompanying drawings when taken in connection with the appended claims.